Question

我正在尝试根据EXIF标签旋转图像。我能够成功处理图像的旋转，但Windows资源管理器中的缩略图仍然是颠倒的。打开时的图像绝对没问题。已验证更正的方向here.以下代码的问题在于EXIF数据似乎没有任何有关缩略图方向的信息。我想要的是：

如果有可用的缩略图方向，请旋转缩略图并更新图像的元数据以进行缩略图方向。
如果没有可用的缩略图方向信息，请旋转缩略图并添加图像的元数据以进行缩略图方向。

我使用的代码是：

public static RotateFlipType RotateImageByExifOrientationData(Image img, string oldFileName, string sourceFilePath, out string newFileName)
{    
    int orientationId = 0x0112;//Image orientation
    int thumbnailOrientationId = 0x5029;//Thumbnail orientation
    var fType = RotateFlipType.RotateNoneFlipNone;

    if (img.PropertyIdList.Contains(orientationId))
    {
        var pItem = img.GetPropertyItem(orientationId);
        //Get the orientation
        fType = GetRotateFlipTypeByExifOrientationData(pItem.Value[0]);
        if (fType != RotateFlipType.RotateNoneFlipNone)
        {
            img.RotateFlip(fType);

            // Read orientation tag. Update to normal so that the other clients(image viewer or browser) will not rotate the rotated image.                                      
            // Force value to 1
            pItem.Value = BitConverter.GetBytes((short)1);
            img.SetPropertyItem(pItem);
            PropertyItem thumbnailItem;
            if (img.PropertyIdList.Contains(thumbnailOrientationId))
            {
                //If thumbnail metadata is available, update it.
                thumbnailItem = img.GetPropertyItem(thumbnailOrientationId);
                thumbnailItem.Value = BitConverter.GetBytes((short)1);
                img.SetPropertyItem(thumbnailItem);
            }
            else
            {
                //If thumbnail metadata is not available, add appropriate metadata.
                thumbnailItem = img.PropertyItems[0];
                thumbnailItem.Id = thumbnailOrientationId;
                thumbnailItem.Type = 2;
                thumbnailItem.Value = BitConverter.GetBytes((short)1);
                thumbnailItem.Len = thumbnailItem.Value.Length;
                img.SetPropertyItem(thumbnailItem);
            }
            newFileName = "Rotated_" + oldFileName;
            string targetFilePath = sourceFilePath + newFileName ;
            ImageFormat targetFormat = ImageFormat.Jpeg;
            img.Save(targetFilePath, targetFormat);
            File.Delete(sourceFilePath + oldFileName);//Delete old file.
        }
    }
    return fType;
}

Answer 1

是一个老问题，但经过一些研究，我注意到即使在删除图像的方向（0x0112）和缩略图的方向（0x5029）后，当再次尝试生成缩略图时，仍然保持相同的方向。所以我检查了一些JPG的缩略图“嵌入”字节。所以删除字节（0x501B）后，我能够正确生成缩略图。

简单代码显示：

    var rotateImage = Image.FromStream(fileStream);
    switch (degree)
    {
        case eRotateImagem.Degree_90:
            rotateImage.RotateFlip(RotateFlipType.Rotate90FlipNone);
            break;
        case eRotateImagem.Degree_180:
            rotateImage.RotateFlip(RotateFlipType.Rotate180FlipNone);
            break;
        case eRotateImagem.Degree_270:
            rotateImage.RotateFlip(RotateFlipType.Rotate270FlipNone);
            break;
    }

    int orientationId = 0x0112; //Image orientation
    int thumbnailOrientationId = 0x5029; //Thumbnail orientation
    int thumbnailBytes = 0x501B; //Thumbnail bytes

    if (rotateImage.PropertyIdList.Contains(orientationId))
    {
        rotateImage.RemovePropertyItem(orientationId);
    }
    if (rotateImage.PropertyIdList.Contains(thumbnailOrientationId))
    {
        rotateImage.RemovePropertyItem(thumbnailOrientationId);
    }
    if (rotateImage.PropertyIdList.Contains(thumbnailBytes))
    {
        rotateImage.RemovePropertyItem(thumbnailBytes);
    }

图像旋转但缩略图不是

1 个答案: